Device for automatically regulating the concentration of developing solution

ABSTRACT

A device for automatically regulating the concentration of a developing solution, consisting of toner dispersed in a carrier solution, maintains developing solution having a predetermined concentration in a wet type developing device. The concentration of the solution is photoelectrically detected, and, when the concentration decreases to less than the predetermined valve concentrated toner from a container is supplied by negative pressure generated by the falling of developing solution then remaining in a concentration regulating device into a developing solution reservoir under the action of gravity. Such concentration adjustment occurs in response to the interruption of the circulation of the solution and disconnection of the concentration regulating device from the surrounding atmosphere.

United States Patent Hosoe et al.

[151 3,650,196 [451 Mar. 21, 1972 [72] inventors: Kazuya Hosoe;Yoshimasa Kimura, both of Tokyo, Japan [73] Assigneez Canon KabushikiKaisha, Tokyo, Japan [22] Filed: Oct. 23, 1969 21 Appl. No.: 868,791

[58] Field ofSearch ..355/10; 95/89; 118/637 XL, 118/9; 117/37 XL [56]References Cited UNITED STATES PATENTS 3,282,177 11/1966 Stanton..355/l0 3,354,802 11/1967 Doucette et a]. ..355/l0 3,369,524 2/1968Fuhrer ..118/637 L X 3,381,662 5/1968 Kolb et al. ..l17l37 L X 3,494,3282/1970 Maloney ..1 18/637 L X Primary Examiner-Samuel S. MatthewsAssistant Examiner-Richard M. Sheer Attorney-Watson, Leavenworth andKeiton [5 7] ABSTRACT A device for automatically regulating theconcentration of a developing solution, consisting of toner dispersed ina carrier solution, maintains developing solution having a predeterminedconcentration in a wet type developing device. The concentration of thesolution is photoelectrically detected, and, when 'the concentrationdecreases to less than the predetermined valve concentrated toner from acontainer is supplied by negative pressure generated by the falling ofdeveloping solution then remaining in a concentration regulating deviceinto a developing solution reservoir under the action of gravity. Suchconcentration adjustment occurs in response to the interruption of thecirculation of the solution and disconnection of the concentrationregulating device from the surrounding atmosphere.

8 Claims, 2 Drawing Figures DEVICE FOR AUTOMATICALLY REGULATING THECONCENTRATION OF DEVELOPING SOLUTION The present invention generallyrelates to electrophotographic devices and particularly to a wet typedeveloping device used in electrophotographic devices. Morespecifically, the present invention relates to an automatic developingsolution concentration regulating device for use with wet typedeveloping devices.

ln electrophotographic processes, the developing solution, consisting oftoner dispersed in a carrier solution, is applied to the exposed surfaceof a photosensitive element for develop ing an electrostatic latentimage formed thereupon. The toner particles are attracted to and heldupon the surface of the photosensitive element in correspondence withthe pattern of the latent image by electrostatic force. Such developedelectrophotographic toner image is fused upon the photosensitive elementby fixing means, such as a heater. Alternately, the developed image maybe transferred to and fused upon a suitable recording element such as apaper sheet. In the wet type developing method used in theelectrophotographic process, toner concentration is decreased as thedeveloping operations are repeated and the concentration of thedeveloping solution must be maintained at a predetermined value so as toenable the production of copies having high quality images without anyirregular adhesion or attraction of the toner particles. As describedabove, the developing solution consists of two components, the tonerparticles and a carrier solution. The toner particles will be consumed,as described above, so that the concentration of the developingsolution, that is, the concentration of the toner particles therein,must be detected and toner supplied for maintaining a predeterminedconcentration during the developing operation.

ln the conventional automatic concentration regulating device for usewith wet-type developing devices for electrophotography, theconcentration of the developing solution is photoelectrically detectedand toner concentrate is supplied or added to the developing solutionfrom a concentrated toner storage container depending upon the detectedconcentration. For example, toner concentrate is added to the developingsolution from an inverted concentrated toner storage container byopening and closing the toner supply opening thereof, thereby droppingthe toner concentrate into the developing solution. In this case, it isvery difficult to add the toner concentrate in exact quantity inresponse to detected concentration and, in some cases, there is thepossibility that toner concentrate may be forced into the developingsolution because of thermal expansion of air inside the storagecontainer. There has been proposed another method in which theconcentrated toner storage container is arranged upright and air underpressure is forced into the container through an air port formed in theupper portion thereof, thereby forcing the toner concentrate out of thecontainer through a toner concentrate supply port formed also in theupper portion thereof. In this case, it is also very difficult to addthe toner concentrate in exact quantity. Furthermore, an air pump mustbe provided for introducing air under pressure into the storagecontainer and the device must be designed to operate with a high degreeof accuracy, thus resulting in high manufacturing cost. In still anothermethod an air port and a toner concentrate supply port are formed in theupper portion of a concentrated toner storage container and a pump isprovided to pump toner concentrate therefrom. However, it is alsodifiicult to add the toner concentrate in exact quantity and there isthe possibility that the pump and its piping may become clogged withtoner particles.

The primary object of the present invention is to provide an automaticdeveloping solution concentration regulating device which can constantlysupply developing solution having a predetermined concentration to a wettype developing device.

Another object of the present invention is to provide an improvedautomatic developing solution concentration regulating device which candetect the toner concentration and constantly maintain it at apredetermined value by supplying toner concentrate or the like dependingupon detected concentration.

A further object of the present invention is to provide an improvedautomatic developing solution concentration regulating device which canpositively circulate developing solution between a developing solutionreservoir and a developing solution container (in a developing device)by use of a pump.

A still further object of the present invention is to provide animproved automatic developing solution concentration regulating devicewhich can effect its whole operations automatically with a high degreeof accuracy based upon static hydrodynamic principles.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description ofone illustrative embodiment thereof taken in conjunction withaccompanying drawing, in which:

FIG. 1 is a longitudinal sectional view of one embodiment of anautomatic developing solution concentration regulating device inaccordance with the present invention; and

FIG. 2 is a circuit diagram of a developing solution concentrationdetecting device used therein.

Referring to FIG. 1, within a developing solution reservoir 1 iscontained a developing solution, consisting of toner dispersed in acarrier solution, and a developing solution circulating pump 3 isdisposed securely in position within the developing solution reservoir 1below the level of the developing solution therein. At the bottom of thecirculation pump 3 is formed an aperture or port 4 for the suction ofthe developing solution therein and two pipes or ducts 5 and 6 forsupplying the developing solution extend upwardly from the upper portionof the circulation pump 3. The pipe 5 is adapted to supply thedeveloping solution into a developing solution tank '8 or the likedisposed within a developing device 7, from which the developingsolution may be returned to the reservoir l. The pipe 6 communicateswith a developing solution concentration regulating tank 9 so that thedeveloping solution discharged from the circulation pump 3 is circulatedthrough the pipe 6, the regulating tank 9, a discharge pipe 10 extendingdownwardly from the regulating tank 9 to the developing solutionreservoir 1. Preferably, the lower open end of the discharge pipe 10 isslightly above the level of the developing solution in the solutionreservoir 1 so that the level, that is the volume of the developingsolution in the developing solution reservoir 1, may be determineddepending upon the position of the lower open end of the discharge pipe10.

Within the developing solution concentration regulating tank 9 isdisposed a photoelectric transducer means 13 consisting of a lightsource 11, connected to a supply E by a switch S, and a photoconductorelement 12. When the concentration of the developing solution risesabove a predetermined value, the developing solution is circulated fromthe reservoir 1 through the circulation pump 3, the developing solutionconcentration regulating tank 9 and the discharge pipe 10 to thereservoir 1 again. On the other hand, when the concentration of thedeveloping solution falls below the predetermined value, signalsindicating this decrease in concentration of the developing solution andgenerated by the photoelectric transducer means are transmitted to anelectromagnet 14 disposed above the concentration regulating tank 9,thereby energizing this electromagnet 14 so as to close a valve 16 in apipe 15, connected between the concentration tank and the surroundingatmosphere and to close a valve 17 between the duct 6 and theconcentration regulating tank 9, thereby opening a circulation pipe 18.

The head between the normal level of the solution within theconcentration regulating tank 9 and the lower opening end of thedischarge pipe 10 is designated by H The head between the average heightdesignated by the line A-B connecting the vertices of a siphon 20intercommunicating the concentration regulating tank 9 and a tonerstorage tank 19 and the level of the toner solution within the tonerstorage tank 19 is designated by H The head between the upper wall ofthe concentration regulating tank 9 and the above described line A-B isdesignated by H In this case, it should be noted that the parts of thedevice of the present invention are so arranged that the followingrelation will be held:

H H H,

Therefore, the developing solution present in the concentrationregulating tank 9 flows down into the developing solution reservoir 1through the discharge pipe 10 by the action of gravity of head H so thata negative pressure is produced in the concentration regulating tank 9.Thus, because of the relation:

H H the toner concentrate within the toner storage tank 19 is forcedinto the concentration regulating tank 9 through the siphon 20, whosebottom end is disposed in closely. spaced apart relation with the bottomof the toner storage tank 19, which is hermetically closed except for avent 21 in the cover thereof. When the toner solution is supplied intothe concentration regulating tank 9 in the manner as describedhereinabove, the pressure within the tank 9 is increased and the tonersolution is mixed with the developing solution. Thereafter, the mixeddeveloping solution flows into the reservoir 1. Thus, it is seen thatwhen the above described steps occur, the concentration of thedeveloping solution may gradually approach a predetermined value. Whenthe developing solution concentration reaches such predetermined value,the photoelectric means is deenergized and the electromagnet 14 is alsodeenergized thereby returning the valves 16 and 17 to their normalpositions. In this case, it should be noted that the flow of the tonersolution from the toner storage tank 19 through the siphon 20 stops 4432H Next referring to FIG. 2, when the concentration of the developingsolution is above the predetermined value, the light emitted by thelight source 11 will not be incident upon the photoconductor element 12,such as CdS, and the element because of the relation:

H has a 3. resistance, as is well known in the art. Therefore, in thetransistorized balancing circuit, the potentials at the points A and Bare substantially equal. Since the transistors Tr and Tr aretemperature-responsive, that is their characteristics are easilysusceptible to variations due to temperature change, a thermistor Th isinterconnected, thereby compensating for the variation due to thetemperature change. When the concentration of the developing solutiondrops below the predetermined level, the light from the light source 11is incident upon the element 12 so that its resistance is decreased.Consequently, the current flowing from the point A into the transistorTr and the resistor r;, is decreased and current flows from the point Cthrough the transistor Tr and a resistor 5 into the transistor Tr andthe resistor r Furthermore, current flows through the electromagnet 14and the transistor Tr so that the electromagnet 14 is energized, therebyclosing the valve 17 so as to close the passage 23 between the pipe 6and the concentrating regulating tank 9 while opening the circulationpipe 18. An armature 22 is attracted by the electromagnet 14 so that thevalve 16 closes the pipe thereby interrupting the interior of theconcentration regulating tank 9 and the surrounding atmosphere.

In the instant embodiment shown in FIG. 1, the photoelectric means 13has been described as being disposed within the concentration regulatingtank 9, but it is understood that it may be disposed within thedeveloping solution reservoir 1 or the developing device 7 as desired.

From the foregoing, it will be understood that the present invention isbased upon static hydraulics principles, in which the concentration ofthe developing solution circulating between the developing device andthe developing solution reservoir is photoelectrically detected so thatwhen the concentration falls below a predetermined value, normalcirculation of the developing solution is stopped and toner solution issupplied from a concentrated toner storage container into theconcentration regulating tank under the influence of the negativepressure produced therein due to gravity flowdown of the developingsolution remaining in the tank 9. Thus devices in accordance with thepresent invention are very simple in construction yet highly reliable inoperation for supplying and constantly maintaining the concentration ofthe developing solution at a predetermined value because the tonerconcentrate may be supplied in exact quantity to maintain theconcentration of the developing solution at the predetermined value.Therefore, better quality copies may be continually provided.

What is claimed is:

1. An automatic developing solution concentration regulating devicecomprising:

a developing solution reservoir;

a developing solution concentration regulating means in communicationwith the surrounding atmosphere;

a toner concentrate storage container;

means for circulating the developing solution between said developingsolution reservoir and said developing solution concentration regulatingmeans when the concentration of the developing solution is higher than apredetermined value;

means for detecting the concentration of the developing solution;

means for interrupting the circulation of the developing solutionthrough said concentration regulating means when the concentration ofthe developing solution decreases to less than said predetermined value;

means for disconnecting the communication of said concentrationregulating means with the surrounding atmosphere; and

means for supplying toner concentrate from said toner concentratestorage container to said concentration regulating means only upon thedecreasing pressure generated by the falling of the developing solutionremaining in said concentration regulating means into said developingsolution reservoir under the action of gravity in response to saidinterruption of the circulation of the developing solution and saiddisconnection of said communication of said concentration regulatingmeans with the surrounding atmosphere.

2. The automatic developing solution concentration regulating deviceclaimed in claim 1 wherein said means for detecting the concentration ofthe developing solution is a photoelectric means providing electricalsignals indicative of variations in intensity of light emitted from alight source due to the variations in concentration of the developingsolution.

3. The automatic developing solution concentration regulating deviceclaimed in claim 1 including means for concurrently actuating said meansfor interrupting the circulation of the developing solution through saidconcentration regulating means and said means for disconnecting thecommunication of said concentration regulating means with thesurrounding atmosphere when the concentration of the developing solutiondecreases to less than said predetermined value.

4. The automatic developing solution concentration regulating deviceclaimed in claim lwherein said means for supplying toner concentratefrom said toner concentrate storage container to said concentrationregulating means is a siphon.

5. The automatic developing solution concentration regulating deviceclaimed in claim 2 including an electromagnet and means for energizingsaid electromagnet where said signals indicate a decrease of theconcentration of the developing solution to below said predeterminedvalue, said electromagnet concurrently actuating said means forinterrupting the circulation of the developing solution through saidconcentration regulating means and said means for disconnecting thecommunication of said concentration regulating means with thesurrounding atmosphere.

6. An automatic developing solution concentration regulating devicecomprising:

a developing device;

a developing solution reservoir;

developing solution concentration regulating means in communication withthe surrounding atmosphere; a toner concentrate storage container; meansfor circulating the developing solution between said developing solutionreservoir and said developing device;

means for circulating the developer solution between said reservoir andsaid developing solution concentration regulating means when theconcentration of the developing solution is higher than a predeterminedvalue;

means for detecting the concentration of the developing solution;

means for interrupting the circulation of the developing solutionthrough said concentration regulating means when the concentration ofthe developing solution decreases to less than said predetermined value;

means for disconnecting the communication of said concentrationregulating means with the surrounding atmosphere; and

means for supplying toner concentrate from said toner concentratestorage container to said concentration regulat ing means only upon thedecreasing pressure generated by the falling of the developing solutionremaining in said concentration regulating means into said developingsolution reservoir under the action of gravity in response to saidinterruption of the circulation of the developing solution and saiddisconnection of said communication of said concentration regulatingmeans with the surrounding atmosphere.

7. The automatic developing solution concentration regulating deviceclaimed in claim 6, wherein said means for detecting the concentrationof the developing solution is disposed in said developing solutionconcentration regulating means.

8. Apparatus for use in maintaining a predetermined concentration oftoner in developing solution contained in a reservoir, comprising:

a vessel containing concentrated toner and having a first portcommunicating with ambient atmosphere and a second port;

a tank having a top wall disposed vertically above the level of toner insaid vessel and including a first tank port and a second tank port, abottom wall providing a third tank port disposed vertically below saidtoner level and a side wall including a fourth tank port;

toner supply means sealably connecting said vessel second port and saidtank second port and extending into said vessel below said toner level;

developing solution circulating means comprising a pump disposed in saidreservoir, a first valve in said tank, a first conduit extending fromsaid pump to said first valve, and a second conduit extending from saidfirst valve to said reservoir;

a second valve connecting said first tank port to ambient atmosphere;

means for detecting the concentration of toner in developing solution insaid tank; and

circuit means responsive to said detecting means for actuating saidfirst and second valves to first positions to provide communicationrespectively between said first con duit and said tank and between saidtank first port and ambient atmosphere when detected toner concentrationis greater than said predetermined concentration and for actuating saidfirst and second valves respectively to second positions to providecommunication between said first conduit and said second conduit and todiscontinue communication between said tank first port and ambientatmosphere when detected toner concentration is less than saidpredetermined concentration.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3650.196 Dated March 21, 1972 lnventofls) Kazuya Hosoe and YoshimasaKimura It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 3, line 31, delete "4432" and insert --because of the relation: H

Column 3, lines 3637, delete "because of the relation: H

has a 3." and insert --l2 accordingly has a'relatively high--.

Column 3, line 59, after "interrupting" insert "communication I betweeSigned and Scaled this 7 Nineteenth D3) Of April 1977 [SEAL] Arrest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner of Parentsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 9Patent No. 3 550 196 Dated March 21, 1972 n n fl Kazuva Hosoe andYoshimasa Kimura It' is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 31, delete "4432" and insert --because of the relation: H

0 Column 3, lines 36-37, delete "because of the relation: H

has a 3." and insert --l2 accordingly has a relatively high-- Column 3,line 59, after "interrupting" insert "communication I between-- Signedand Scaled this 0 I Nineteenth Day of 1x 5511 77 [SEAL] A ttes I:

. RUTH c. MASON c. MARSHALL DANN AIM-Wing Office Commissioner oj'Patentsand 'Trademarks

1. An automatic developing solution concentration regulating devicecomprising: a developing solution reservoir; a developing solutionconcentration regulating means in communication with the surroundingatmosphere; a toner concentrate storage container; means for circulatingthe developing solution between said developing solution reservoir andsaid developing solution concentration regulating means when theconcentration of the developing solution is higher than a predeterminedvalue; means for detecting the concentration of the developing solution;means for interrupting the circulation of the developing solutionthrough said concentration regulating means when the concentration ofthe developing solution decreases to less than said predetermined value;means for disconnecting the communication of said concentrationregulating means with the surrounding atmosphere; and means forsupplying toner concentrate from said toner concentrate storagecontainer to said concentration regulating means only upon thedecreasing pressure generated by the falling of the developing solutionremaining in said concentration regulating means into said developingsolution reservoir under thE action of gravity in response to saidinterruption of the circulation of the developing solution and saiddisconnection of said communication of said concentration regulatingmeans with the surrounding atmosphere.
 2. The automatic developingsolution concentration regulating device claimed in claim 1 wherein saidmeans for detecting the concentration of the developing solution is aphotoelectric means providing electrical signals indicative ofvariations in intensity of light emitted from a light source due to thevariations in concentration of the developing solution.
 3. The automaticdeveloping solution concentration regulating device claimed in claim 1including means for concurrently actuating said means for interruptingthe circulation of the developing solution through said concentrationregulating means and said means for disconnecting the communication ofsaid concentration regulating means with the surrounding atmosphere whenthe concentration of the developing solution decreases to less than saidpredetermined value.
 4. The automatic developing solution concentrationregulating device claimed in claim 1 wherein said means for supplyingtoner concentrate from said toner concentrate storage container to saidconcentration regulating means is a siphon.
 5. The automatic developingsolution concentration regulating device claimed in claim 2 including anelectromagnet and means for energizing said electromagnet where saidsignals indicate a decrease of the concentration of the developingsolution to below said predetermined value, said electromagnetconcurrently actuating said means for interrupting the circulation ofthe developing solution through said concentration regulating means andsaid means for disconnecting the communication of said concentrationregulating means with the surrounding atmosphere.
 6. An automaticdeveloping solution concentration regulating device comprising: adeveloping device; a developing solution reservoir; developing solutionconcentration regulating means in communication with the surroundingatmosphere; a toner concentrate storage container; means for circulatingthe developing solution between said developing solution reservoir andsaid developing device; means for circulating the developer solutionbetween said reservoir and said developing solution concentrationregulating means when the concentration of the developing solution ishigher than a predetermined value; means for detecting the concentrationof the developing solution; means for interrupting the circulation ofthe developing solution through said concentration regulating means whenthe concentration of the developing solution decreases to less than saidpredetermined value; means for disconnecting the communication of saidconcentration regulating means with the surrounding atmosphere; andmeans for supplying toner concentrate from said toner concentratestorage container to said concentration regulating means only upon thedecreasing pressure generated by the falling of the developing solutionremaining in said concentration regulating means into said developingsolution reservoir under the action of gravity in response to saidinterruption of the circulation of the developing solution and saiddisconnection of said communication of said concentration regulatingmeans with the surrounding atmosphere.
 7. The automatic developingsolution concentration regulating device claimed in claim 6, whereinsaid means for detecting the concentration of the developing solution isdisposed in said developing solution concentration regulating means. 8.Apparatus for use in maintaining a predetermined concentration of tonerin developing solution contained in a reservoir, comprising: a vesselcontaining concentrated toner and having a first port communicating withambient atmosphere and a second port; a tank having a top wall disposedvertically above the level of toner in said vessel and including a firsttank port and a second tank port, a bottom wall providing a third tankport disposed vertically below said toner level and a side wallincluding a fourth tank port; toner supply means sealably connectingsaid vessel second port and said tank second port and extending intosaid vessel below said toner level; developing solution circulatingmeans comprising a pump disposed in said reservoir, a first valve insaid tank, a first conduit extending from said pump to said first valve,and a second conduit extending from said first valve to said reservoir;a second valve connecting said first tank port to ambient atmosphere;means for detecting the concentration of toner in developing solution insaid tank; and circuit means responsive to said detecting means foractuating said first and second valves to first positions to providecommunication respectively between said first conduit and said tank andbetween said tank first port and ambient atmosphere when detected tonerconcentration is greater than said predetermined concentration and foractuating said first and second valves respectively to second positionsto provide communication between said first conduit and said secondconduit and to discontinue communication between said tank first portand ambient atmosphere when detected toner concentration is less thansaid predetermined concentration.